Uncontrolled seed transfer and the use of material
of unknown origin pose threats to the adaptedness and
adaptive potential of tree plantations. Legal regulations
rule the marketing and use of forest reproductive
material in industrialized countries (Muhs, 1996).
However, in Central Europe patterns of genetic variation
of the most important tree species, in particular
conifers, were irreversibly modified by long-distance
transport of seeds for centuries before these regulations
were implemented (Stern, 1968), and comparable
regulations do not exist or are not enforced in
most developing countries. Thus, the use of material of
unknown origin for plantation establishment continues
to be one of the most severe impacts on genetic
structures of forest trees imposed by forest managers
in many parts of the world (Stern, 1968). Circumstantial
evidence often points towards low levels of genetic
variation of reproductive material if the origin is
unknown (Sim, 1984). One of the few studies aimed
at investigating the genetic consequences of uncontrolled
seed transfer for a tropical plantation species is
described in case study 1.